1. Field of the Invention
The invention relates to a gear mechanism part for a cable-controlled window lifter as well as to a drive unit for a cable-controlled window lifter.
2. Description of the Background Art
A cable-controlled window lifter is used to raise and lower a window of a motor vehicle. A cable-controlled window lifter of this type is known, for example, from EP 1 617 028 A1. The cable-controlled window lifter described therein has two guide rails, along each of which a driver is movably mounted. The window pane is attached to the two drivers. A cable pull, which may be driven by a drive unit, is also pivoted to the driver. The cable of the cable pull is partially wound onto a cable drum, which is drivable by the drive unit and is provided with a cable groove. With the aid of the drive unit, either both drivers—and thus the window pane—are moved up, or if the driving direction is reversed, both drivers—and thus the window pane—are moved down. Cable-controlled window lifters having only one guide rail and one driver are also known.
Driving the cable drum with the aid of a gear wheel driven by the drive unit is known in the conventional art. In this regard, the gear wheel and cable drum are disposed on a common axis. The gear wheel and cable drum are coupled to each other by positive fit between an outer gearing disposed on an inner circumferential projection and an inner gearing disposed on an outer circumferential projection. At least one fitting chamber is introduced into the cable drum for fastening the cable ends. For this purpose, the cable end has a fitting which is inserted into the fitting chamber during mounting. Dividing the gear mechanism part between the gear wheel and the cable drum simplifies mounting the cable pull wound on the cable drum. The cable drum having the cable attachment may be removed for mounting the gear wheel. In this regard, the drive unit, guide rail, deflection roller and driver my be premounted on the cable-controlled window lifter.
During final mounting, only the cable needs to be attached to the driver and to the cable drum and the cable drum coupled to the gear wheel. In this manner, it is possible to replace a defective drive unit easily, quickly and without problems.
Separating the gear wheel and cable drum also makes it possible to use different materials, optimized to the particular application, for the gear wheel and the cable drum. The gear wheel, in particular, may be made of a strong, wear-resistant and lubricant-resistant plastic, which has a long service life under mechanical load. The cable drum, in particular, is made of a plastic having good static friction properties, lending the cable guidance a high coefficient of friction and practically preventing the cable from twisting or even being dislodged from its cable groove.